Nov. 13 update: The latest update from the U.S. Centers for Disease Control and Prevention (CDC) puts this outbreak at 50 total illnesses: 31 people in Washington state and 19 in Oregon. That is an increase of one more case of E. coli infection reported from Washington.

The Oregon Health Authority, however, is reporting 18 E. coli cases (both confirmed and presumptive) connected with this outbreak as of Nov. 13.

CDC stated in its Nov. 12 outbreak update that 33 isolates from those sickened (22 in WA and 11 in OR) have been uploaded to the agency’s PulseNet database, and all of them were infected with Shiga toxin-producing E. coli O26 (STEC) having the same DNA fingerprint.

CDC noted that the ill person in Minnesota previously reported as having a STEC O26 infection with the same DNA fingerprint did not eat at a Chipotle Mexican Grill in the week before becoming ill. That case does not appear related to the WA and OR outbreak linked to Chipotle locations in those states, the agency added.

Meanwhile, CDC and state and local public health partners are continuing laboratory surveillance through PulseNet to identify additional ill persons and to interview them. Updates will be provided when more information is available, CDC stated.

Also, the investigation is still ongoing to determine if the ill people ate a meal item or ingredient in common served at the identified Chipotle Mexican Grill locations. Several food items collected from Chipotle Mexican Grill locations in Washington and Oregon are being tested by the U.S. Food and Drug Administration (FDA) and Chipotle for the presence of bacteria.

As of Nov. 12, test results have not identified E. coli in any of the food items tested, CDC stated, adding that other results are pending and will be reported once they are available.

On Wednesday, Nov. 11, Chipotle began reopening its restaurants in Washington and multiple locations in the Portland, OR, area that had been closed since Oct. 30 in response to the outbreak. Most restaurants have been reopened, with the others reopening in the coming days. Chipotle agreed to carry out a range of food safety actions recommended by Washington and Oregon before reopening these restaurant locations, CDC stated.

Previous coverage follows:

Chipotle Mexican Grill plans to start reopening 14 restaurants in Oregon and 29 in Washington which it closed down Oct. 31 following an E. coli outbreak. Company spokesman Chris Arnold said that the 43 shuttered outlets will begin doing business again on Wednesday, Nov. 11.

At least 49 people (3o in WA and 19 in OR) were sickened and 14 were hospitalized in the outbreak, and 11 of the company’s “fast casual” restaurants in OR and WA were the common denominator among some of those who became ill. No deaths or cases of hemolytic uremic syndrome (HUS), a dangerous complication from E. coli infection, have been reported.

According to the U.S. Centers for Disease Control and Prevention (CDC), the same strain of Shiga toxin-producing E. coli O26 with the same DNA fingerprint infected 23 of those sickened. However, laboratory testing by the U.S. Food and Drug Administration (FDA) and the company found no E. coli O26 bacteria in food samples taken from the restaurants.

CDC also reported that a search of its PulseNet database identified one person in Minnesota infected with STEC O26 having the same DNA fingerprint. However, this person did not eat at a Chipotle Mexican Grill in the week before becoming ill.

“The illness does not appear to be related to the outbreak in Washington and Oregon linked to Chipotle Mexican Grill locations in those states,” CDC noted, adding that the Minnesota investigation is continuing.

In the 10 days since closing down the 43 OR and WA restaurants, the company has done extensive cleaning and sanitizing and replaced all food ingredients with fresh items.

“The safety of our customers and integrity of our food supply has always been our highest priority,” Chipotle CEO Steve Ells stated. “If there are any opportunities for us to do better in any facet of our sourcing or food handling — from the farms to our restaurants — we will find them.”

On Tuesday, Nov. 10, Chipotle announced that it has hired two independent consulting firms to “identify any possible improvements in our food safety practices” and has taken steps to make sure that all food products, food surfaces and restaurant equipment are free of foodborne pathogens.

The source of the outbreak is still a mystery, although there has been speculation that contaminated produce — such as lettuce, tomatoes, onions, salsa or cilantro — may have been the culprit.

The Washington State Department of Health stated that, as of Nov. 9, the most recent person sickened in the outbreak reported eating at a Chipotle restaurant on Oct. 24.

“While health officials believe the risk for new exposures is very low, the number of cases in the outbreak may rise or fall as pending lab tests determine if more ill people have this specific strain of E. coli infection. In Washington, four tests are still in progress,” the department stated.

The Oregon Health Authority (OHA) announced Monday, Nov. 9, that public health officials had made several recommendations to Chipotle about actions to take before reopening its closed-down restaurants there. OHA indicated that the company had accepted the following suggestions:

Every Chipotle in the state will dispose of all food items, sanitize each facility, and bring in all new foods before reopening.

Selected high-risk food items will be pretested before heading to the restaurants.

All fresh produce will be carefully rinsed and sanitized.

County public health food safety inspectors will visit each restaurant to verify these actions.

Several lawsuits have been filed by people who say they were sickened in the outbreak.